What is root in AS3?

Question

Hi guys,
for example, in this .as file, what is root? And "this" is a reference to the class?
ps. This .as is connected with a .fla
package  {
    import flash.display.MovieClip;
    import flash.events.Event;
    public class FlashVars extends MovieClip {
        public function FlashVars() {
            carregarFlashVars ();
        private function carregarFlashVars (): void {
            this.root.loaderInfo.addEventListener (Event.COMPLETE, mostrarValor);
        private function mostrarValor (e: Event): void {
            texto_txt.text = e.target.parameters.nome;

Answer 1

"But if the SWF is loaded into another SWF, root becomes the hosting SWF."
This is not true. root is the same for the same swf and doesn't change even when it is loaded into another swf.
Here are three classes that will demonstrate it. Just compile them into the same directory with respective names. When GrandParent swf is run the following traces are displayed:
[object GrandParent] root = [object GrandParent]
[object Parent] root = [object Parent]
[object Child] root = [object Child]
Which, again, shows that root did not change.
package
     import flash.display.Loader;
     import flash.display.Sprite;
     import flash.events.Event;
     import flash.net.URLRequest;
     public class GrandParent extends Sprite
          public function GrandParent()
               if (stage) init();
               else addEventListener(Event.ADDED_TO_STAGE, init);
          private function init(e:Event = null):void
               removeEventListener(Event.ADDED_TO_STAGE, init);
               trace(this, "root =", root);
               var loader:Loader = new Loader();
               loader.load(new URLRequest("parent.swf"));
               addChild(loader);
package
     import flash.display.Loader;
     import flash.display.Sprite;
     import flash.events.Event;
     import flash.net.URLRequest;
     public class Parent extends Sprite
          public function Parent()
               if (stage) init();
               else addEventListener(Event.ADDED_TO_STAGE, init);
          private function init(e:Event = null):void
               removeEventListener(Event.ADDED_TO_STAGE, init);
                        trace(this, "root =", root);
               var loader:Loader = new Loader();
               loader.load(new URLRequest("child.swf"));
               addChild(loader);
package
     import flash.display.Sprite;
     import flash.events.Event;
     public class Child extends Sprite
          public function Child()
               if (stage) init();
               else addEventListener(Event.ADDED_TO_STAGE, init);
          private function init(e:Event = null):void
               removeEventListener(Event.ADDED_TO_STAGE, init);
               trace(this, "root =", root);